Drinking water treatment is the process of turning river water into drinking water. Raw water can come from groundwater or surface water and is not always drinkable without treatment.

What results into drinking water treatment?
Many compounds must be removed before the water can be drunk. Indeed, raw water is cloudy and contains pollutants, pesticides, organic molecules that can be toxic for human beings. These elements come from soil, dissolution of rocks, anthropic activities (industry, agriculture…). It is therefore necessary to carry out numerous physical and chemical treatments in order to have good quality water that meets the standards in force.

The amount of treatment needed depends on the initial quality of the raw water. Groundwater will need less treatment because the soil will have already filtered this water and thus removed part of the pollution. However, it is more complicated to have an important production.

The Different Steps To Produce Drinking Water:

1) Water goes through physical pretreatment to remove anything that could damage the pumps, valves and other equipment in the drinking water plant. Large elements and sand are removed by a bar screen and a grit chamber.

2) Pre-oxidation: In order to remove mineral compounds (Fe, Mg), unpleasant taste and smell from the water, a strong oxidizer like ozone is used. It also allows to destabilize the dissolved organic matter and some micropollutants to facilitate the coagulation stage.

3) Accidental water pollution: Raw water can be accidentally polluted by pesticides, herbicides, surfactants, hydrocarbons. An injection of powdered activated carbon with a very high adsorbing power allows to eliminate a large part of these toxic elements.

4) Mineralization or Demineralization: Depending on the characteristics of the water, mineralization or demineralization is necessary.

-If the water hardness is too high a demineralization is needed to reduce the amount of Ca2+ and Mg2+ . The reduction of these elements will allow to limit the deposit of limescale that settles in the pipes and can damage water heaters and other household appliances.

-If the aggressiveness of the water is too high, mineralization is carried out to reduce the concentration of carbon dioxide which can attack the pipes and release toxic metals such as lead.

To ovoid these two problems, lime or soda ash is added to the water with different concentrations.